Electric machine and manual machine tool comprising the same

ABSTRACT

The invention is based on an electrical machine with a rotatable brush plate ( 10, 12 ), which is held in its end positions by means of at least one holding mechanism ( 16, 18 ) that acts in the circumference direction ( 14 ). 
     The invention proposes that the holding mechanism ( 16, 18 ) have at least one device ( 20, 22 ) that loads the brush plate ( 10, 12 ) in the circumference direction ( 14 ).

BACKGROUND OF THE INVENTION

The invention is based on an electrical machine.

In electrical machines with a brush plate that can be rotated on ahousing base of a housing part, it is known to hold this brush plate inits end positions by means of a holding mechanism that acts in thecircumference direction. The holding mechanism has hooks formed onto thebrush plate, which engage the housing base from behind and which aremoved in the circumference direction along a radially outward pointingend of the housing base when the brush plate is rotated. The end hasprojections pointing radially outward that are formed onto the housingbase, spaced apart from end stops in the circumference direction. Thedistances between the end stops and the corresponding projections areselected so that they correspond to one hook width. When the brush plateis rotated, the hook moves across the projection extending in the radialdirection, and arrives in an end position between the corresponding endstop and the respective projection. The end stop and the radialprojection secure the brush plate in the circumference direction.

SUMMARY OF THE INVENTION

The invention is based on an electric machine with a rotatable brushplate that is held in its end positions by means of at least one holdingmechanism that acts in the circumference direction.

The invention proposes that the holding mechanism have at least onedevice that loads the brush plate in the circumference direction. Thebrush plate can advantageously be held in a constant, play-free mannerin its respective end position counter to a rotation direction, and awear on the holding mechanism, in particular by outwardly pointingradial projections, can be advantageously avoided. A contact between astrip conductor affixed to the housing and a carbon cartridge mountedonto the brush plate can always be assured in the end positions, whichmakes it possible to prevent contacts from being burned off and toprevent a burn off-induced failure of the electrical machine.

The device advantageously has a bistable position, at least when in theinstalled position. Two forces in opposite directions can be generatedin a structurally simple fashion with a single device or with a smallnumber of components. It is also possible to achieve a design in whichthe device always moves the brush plate from an intermediate region intoone of its end positions.

The device can be comprised of various components deemed appropriate byone skilled in the art, which have a bistable position eitherintrinsically or as a result of their installation, for example a relay,a spring element, etc. If the device is comprised of a spring element,then this permits a structurally simple, durable, reasonably priced, andspace-saving device to be produced.

The spring element can be comprised of various spring elements deemedappropriate by one skilled in the art, e.g. a disk spring, a leg spring,etc. If the spring element is comprised of a leg spring, then aninexpensive, space-saving spring can be used, whose legs canadvantageously be guided into the corresponding recesses disposed in thebrush plate and in a housing part. The leg spring can be supported withits first leg against the housing part and its second leg can exert aspring force on the brush plate in the direction of its end positions.

In another embodiment, the invention proposes that the leg spring besupported so that it can pivot around the first leg. A bistable positionof the leg spring can be achieved in a structurally simple manner and asimple and rapidly mountable holding mechanism can be achieved.

The invention also proposes the possibility of the leg spring engagingin detent fashion with the brush plate by means of a detent element. Theleg spring can advantageously be preinstalled onto the brush plate andsecured to it in captive fashion. The brush plate and the leg spring canbe simply installed and removed as a unit.

If the detent element is of one piece with the leg spring, then thispermits savings with regard to additional components, space, and costs.

At least one leg of the leg spring advantageously has a part forpreventing an incorrect installation. The part can be comprised of aseparate component or can be formed onto one end of the leg and be ofone piece with it. If the part is formed onto the end of the leg of theleg spring-by means of a bending procedure, then a structurally simple,inexpensive protection against incorrect installation can be achieved.

In another embodiment, the invention proposes that an actuating buttonbe embodied of one piece with the brush plate. This permits savings withregard to additional components, space, weight, and assembly costs. Itis also possible for an advantageous installation space for the deviceto be created, particularly in the vicinity of the actuating button.

The invention also proposes that the brush plate be held in its endpositions by means of at least one detent mechanism. The action of thedevice can be assisted and an operator can be clearly notified that therespective end position has been reached by means of a detentengagement.

Other advantages ensue from the following description of the drawings.The drawings depict exemplary embodiments of the invention. Thedrawings, the specification, and the claims contain numerous features incombination. One skilled in the art will suitably also consider thefeatures individually and will unite them in other meaningfulcombinations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematically depicted side view of a drill,

FIG. 2 shows a longitudinal section through a detail 11 in FIG. 1,

FIG. 3 shows a section along the line III—III in FIG. 2,

FIG. 4 shows a section along the line IV—IV in FIG. 2, in a first endposition,

FIG. 5 shows a section along the line IV—IV in FIG. 2, in a second endposition, and

FIG. 6 shows a detail of another exemplary embodiment with analternative holding mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a drill with a housing 38 that has an electric motormounted in it, whose rotation direction 40, or the rotation direction 40of a drill bit 44 clamped in a tool holder 42, can be selected by meansof a reversing lever 46. The reversing lever 46 is disposed above anactuating switch 48 of the drill so that with one hand, an operator canoperate the actuating switch 48, switch the drill on or off, and selectthe desired rotation direction 40 of the drill bit 44 by using thereversing lever 46. On a side of the drill oriented toward the toolholder 42, a first handle 50 extending perpendicular to the actuationdirection is fastened to the housing 38. On a side of the housing 38oriented away from the tool holder 42, a second handle 52 extendingperpendicular to the actuating direction is provided, which constitutesa part of the housing 38.

The reversing lever 46 has an engaging fork 54, whose free endpositively engages with an articulating pin 56 (FIGS. 2, 3, 4, and 5).The articulating pin 56 is formed onto a brush plate 10 in a lowerregion close to the reversing lever 46. The brush plate 10, which issupported in rotary fashion on a housing base 58, radially encloses anarmature shaft 60. The brush plate 10 is secured in the axial directionby means of stays 88, which extend in the axial direction toward thetool holder 42 on a side of the brush plate 10 oriented away from thearmature winding 90 and are formed onto an inside of the handle 52.

Carbon cartridges 80, 80′ are disposed situated diagonally opposite fromeach other on the brush plate 10 (FIGS. 4 and 5). The carbon cartridges80, 80′ have recesses, not shown, for containing carbon brushes 82, 82′.Spring elements 84, 84′ press the carbon brushes 82, 82′ radially inwardagainst a commutator 86 (FIG. 2).

A holding mechanism 16 that acts in the circumference direction 14 holdsthe brush plate 10 in its end positions (FIGS. 3, 4, and 5). The holdingmechanism 16 has a device 20 comprised of a leg spring that has abistable position and that loads the brush plate 10 from a neutral,unstable, middle position, in the circumference direction 14 toward itsrespective end positions. The leg spring 20 has a first leg 24 and asecond leg 66, which are connected to each other by a coil 108 of theleg spring 20.

The leg spring 20 is supported so that it can pivot around thelongitudinal axis of the first leg 24 (FIG. 3). The first leg 24, whoseend 62 points toward the tool holder 42, engages in a longitudinalchannel 64 that is formed into an outer circumference of a cup-shapedinner region of the housing 38 that is encompassed by the handle 52. Thearmature shaft 60 of the electric motor is supported in the cup-shapedregion of the housing 38.

The second leg 66 of the leg spring 20, which also points toward thetool holder 42, has a region that is bent radially outward at its end68. With the bent region, the second leg 66 positively engages in atransverse channel 70 that is formed into a collar 72 on the radialoutside of the brush plate 10.

The leg spring 20 is supported with its first leg 24 in the longitudinalchannel 64 on the housing 38 and with its second leg 66, by means of thetransverse channel 70, presses the brush plate 10 in the circumferencedirection 14, into its first end position (FIG. 4). In the first endposition, the brush plate 10 is also secured in the circumferencedirection by a detent mechanism 36.

The detent mechanism 36 has two detent bolts 74, 74′ formed onto thehousing 38 that are disposed diagonally opposite each other (FIG. 4). Inthe first end position of the brush plate 10, the detent bolts 74, 74′positively engage in detent recesses 76, 76′ that are let into outwardlyprotruding projections that are formed onto the brush plate 10.

If an operator actuates the reversing lever 46, the brush plate 10 isrotated in the circumference direction 14 by means of the engaging fork54 and the articulating pin 56, and the detent bolts 74, 74′ and thedetent recesses 76, 76′ disengage from one another. The leg spring 20 iscompressed by means of its legs 24, 66 until the neutral position isreached. After the neutral position is passed, the leg spring 20 expandsand with its second leg 66, presses the brush plate 10 in thecircumference direction 14, into its second end position and issupported with its first leg 24 in the longitudinal channel 64 of thehousing 38. When the second end position is reached, the detent bolts74, 74′ engage with two other detent recesses 78, 78′ let into theframes 92, 92′ of the carbon cartridges 80, 80′. In addition to the legspring 20, the brush plate 10 is also secured in the circumferencedirection in its second end position by means of the detent bolts 74,74′ and the detent recesses 78, 78′. In addition, a spring-loaded detentbolt 104 in a recess of the engaging fork 54 fixes the reversing lever46 and the engaging fork 54 to the housing 38 in the respective endposition of the brush plate 10 by engaging in recesses of the housing 38in the end positions (FIG. 2).

FIG. 6 shows a detail of an exemplary embodiment with an alternativeholding mechanism 18. In principle, components that remain essentiallythe same are provided with the same reference numerals. Furthermore, forfeatures and functions that remain the same, reference can be made tothe description of the exemplary embodiment in FIGS. 1 to 5. Thedescription below is essentially restricted to the differences from theexemplary embodiment in FIGS. 1 to 5.

The holding mechanism 18 has a device 22 comprised of a leg spring,which has a bistable position and loads the brush plate 12 from aneutral, unstable position, in the circumference direction 14 toward itsrespective end positions. The leg spring 22 has a first leg 26 and asecond leg 34, which are connected to each other by means of a coil 106of the leg spring 22.

The leg spring 22 is supported so that it can pivot around thelongitudinal axis of the first leg 26. The first leg 26 points in thedirection oriented away from a tool holder 42 and engages in alongitudinal channel 94 that is formed into an outer circumference of acup-shaped inner region of a housing 38 that is encompassed by thehandle 52. At its end 100, the first leg 26 has a region that is bentradially outward, which constitutes a part 30 that prevents an incorrectinstallation.

At its end 102, the second leg 34 of the leg spring 22, which alsopoints in the direction oriented away from the tool holder 42, has aregion that is bent radially inward, is embodied as a detent element 28,and has a bent longitudinal axis. An actuating button 32 is formed ontoa radially outer region of the brush plate 12 and protrudes outward fromthe housing 38. The second leg 34 engages in a longitudinal channel 96that is formed into the radially outer region of the brush plate 12.

During installation, the second leg 34 of the leg spring 22 is insertedinto the longitudinal channel 96 by means of a pocket 98 in the brushplate 12, and is elastically deformed in the process. After the end 102of the second leg 34 has crossed the longitudinal channel 96 and whenthe leg spring 22 engages with its coil 106 in the pocket 98, the secondleg 34 expands and the leg spring 22 is fastened to the brush plate 12in captive fashion. The brush plate 12 can be installed in the housing38 together with the preinstalled leg spring 22. In this case, the firstleg 26 of the leg spring 22 is inserted into the open longitudinalchannel 94.

In the installed position, the leg spring 22 is supported on the housing38 with its first leg 26 in the longitudinal channel 94 and with itssecond leg 34, by means of the longitudinal channel 96, presses thebrush plate 12 in the circumference direction 14, into its first endposition.

By means of the actuating button 32 protruding from the side of thehousing 38, an operator can rotate the brush plate 12 in thecircumference direction 14 on a housing base 58. The leg spring 22 iscompressed by means of its legs 26, 34 until the neutral position isreached. After the neutral position is passed, the leg spring 22 expandsand with its second leg 34, presses the brush plate 12 and the actuatingbutton 32 in the circumference direction 14, into their second endposition and is supported with its first leg 26 in the longitudinalchannel 94 of the housing 38.

REFERENCE NUMERALS

-   10 brush plate-   12 brush plate-   14 circumference direction-   16 holding mechanism-   18 holding mechanism-   20 device-   22 device-   24 leg-   26 leg-   28 detent element-   30 part-   32 actuating button-   34 leg-   36 detent mechanism-   38 housing-   40 rotation direction-   42 tool holder-   44 drill bit-   46 reversing lever-   48 actuating switch-   50 handle-   52 handle-   54 engaging fork-   56 articulating pin-   58 housing base-   60 armature shaft-   62 end-   64 longitudinal channel-   66 leg-   68 end-   70 transverse channel-   72 collar-   74 detent bolt-   76 detent recess-   78 detent recess-   80 carbon cartridge-   82 carbon brush-   84 spring element-   86 commutator-   88 stay-   90 armature winding-   92 frame-   94 longitudinal channel-   96 longitudinal channel-   98 pocket-   100 end-   102 end-   104 detent bolt-   106 coil-   108 coil

1. An electrical machine with a rotatable brush plate (10, 12), which isheld in its end positions by means of at least one holding mechanism(16, 18) that acts in the circumference direction (14), characterized inthat the holding mechanism (16, 18) has at least one device (20, 22)that loads the brush plate (10, 12) in the circumference direction (14)in said end positions, wherein said device (20, 22) is comprised of aspring element, said spring element being engaged with the brush plate(10, 12).
 2. The electrical machine according to claim 1, characterizedin that the device (20, 22) has a bistable position, at least in theinstalled position.
 3. The electrical machine according to claim 2,characterized in that the device (20, 22) is comprised of a springelement.
 4. The electrical machine according to claim 3, characterizedin that the device (20, 22) is comprised of a leg spring.
 5. A handmachine tool with an electrical machine according to claim
 1. 6. Anelectrical machine with a rotatable brush plate (10, 12), which is heldin end positions by means of at least one holding mechanism (16, 18)that acts in the circumference direction (14), characterized in that theholding mechanism (16, 18) has at least one device (20, 22) that loadsthe brush plate (10, 12) in the circumference direction (14), whereinsaid device (20, 22) has a bistabile position, at least in the installedposition, wherein said device (20, 22) is comprised of a leg spring andwherein said leg spring (20, 22) is supported so that it can pivotaround a first leg (24, 26).
 7. The electrical machine according toclaim 6, characterized in that the leg spring (22) can engage the brushplate (12) in detent fashion by means of at least one detent element(28).
 8. The electrical machine according to claim 7, characterized inthat the detent element (28) is of one piece with the leg spring (22).9. The electrical machine according to claim 6, characterized in that anactuating button (32) is of one piece with the brush plate (12).
 10. Theelectrical machine according to claim 6, characterized in that at leastone detent mechanism (36) holds the brush plate (10, 12) in its endpositions.
 11. An electrical machine with a rotatable brush plate (10,12) which is held in end positions by means of at least one holdingmechanism (16, 18) that acts in the circumference direction (14),characterized in that the holding mechanism (16, 18) has at least onedevice (20, 22) that loads the brush plate (10, 12) in the circumferencedirection (14), wherein said device (20, 22) has a bistable position, atleast in the installed position, wherein said device (20, 22) iscomprised of a log spring and wherein at least one leg (26) of said legspring (22) has a part (30) that prevents an incorrect installation.